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OpenDarwin 7.2.1 - man page for atan2 (opendarwin section 3)

ATAN2(3)				     BSD Library Functions Manual				     ATAN2(3)

NAME
atan2 -- arc tangent function of two variables
SYNOPSIS
#include <math.h> double atan2(double y, double x);
DESCRIPTION
The atan2() function computes the principal value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the return value.
SPECIAL VALUES
atan2(+-0, -0) returns +-pi. atan2(+-0, +0) returns +-0. atan2(+-0, x) returns +-pi for x < 0. atan2(+-0, x) returns +-0 for x > 0. atan2(y, +-0) returns -pi/2 for y > 0. atan2(+-y, -infinity) returns +-pi for finite y > 0. atan2(+-y, +infinity) returns +-0 for finite y > 0. atan2(+-infinity, +x) returns +-pi/2 for finite x. atan2(+-infinity, -infinity) returns +-3*pi/4. atan2(+-infinity, +infinity) returns +-pi/4.
NOTES
The atan2() function is used mostly to convert from rectangular (x,y) to polar (r,theta) coordinates that must satisfy x = r*cos theta and y = r*sin theta. In general, conversions to polar coordinates should be computed thus: r := hypot(x,y); ... := sqrt(x*x+y*y) theta := atan2(y,x).
SEE ALSO
acos(3), asin(3), atan(3), cos(3), cosh(3), sin(3), sinh(3), tan(3), tanh(3), math(3),
STANDARDS
The atan2() function conforms to ISO/IEC 9899:1999(E).
BSD
November 18, 2002 BSD


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